AERODYNAMICS See also FLUID
DYNAMICS VIDEOS
A very simple wind tunnel using a plastic
sheet rolled into a cone.
It blows air at 4 m/s onto a polystyrene ball supported by two cotton threads (to reduce sideways motion). The angle from the vertical measures
the drag force
Measuring the drag force on a balloon. The forces on the balloon include gravity, the buoyant force and the drag force.
Magnus force on a spinning
balloon. Magnus force on a paper cylinder
Magnus force on two plastic cups taped end to end and launched with backspin using two rubber
bands. The result is a typical baseball “pop-up”. Here is the method and here is a
backspin “golf shot” at lower spin.
Slow motion 300 fps movie showing a 10 gram
polystyrene ball
thrown with a home-made Lacrosse type launcher at 23 m/s with backspin at 2000 rpm. Defies gravity !
The same 10 gram ball launched with sidespin
shows an equally dramatic effect in the horizontal direction due to the horizontal Magnus force. The spin
axis is slightly tilted. The small vertical component of the Magnus force
counters gravity, so the ball moves in a horizontal plane. Another example Even more surprising is Negative Magnus on a smooth ball.
Reverse swing of a cricket ball occurs at
ball speeds around 90 mph, provided
the seam is aligned at around 20-30 degrees to the path of the ball. It can be easily
demonstrated with a balloon at 1 mph